The present invention relates to an improved valve having an improved stem seal which will maintain its seal against high pressures, elevated temperatures and with rotary and axial cycling of the valve stem.
Prior stem seals have utilized inverted U-shaped ring seals having a plurality of sealing lips on the interior and exterior sealing surfaces and with a spring within the opening of the ring to urge the lips outward and inward into sealing engagement. An example of such a seal structure is shown in U.S. Pat. No. 4,103,909. Such seal structure has not been satisfactory because the sealing lips wear responsive to movement, they are not held in their desired sealing position when they are exposed to pressure, and there is no protection against extrusion of the lips.